1. Field of the Disclosure
The invention relates to a surge protection device.
Surge protection devices (SPDs) in particular for the class I range are typically operated in very powerful supply systems. These surge protection devices (SPDs), in the event of an excessive voltage, shunt the current at the devices to be protected, that is to say an arrester is activated.
Pre-fuses, for example low-voltage HBC fuses of type NH01 to NH03, are arranged upstream of the surge protection devices.
The upstream fuses are either installed in the branch to the arrester, that is to say protect only the arrester itself, or are the upstream fuses of the overall system in which the surge protection device is operated.
2. Description of the Related Art
Surge protection devices often contain a number of parallel current paths.
These paths are usually at least one primary discharge current path and one or more secondary or auxiliary current paths.
The primary discharge current paths are intended to conduct the excessive voltages and current pulses and are therefore designed so as to be stable, that is to say with large cross sections.
The secondary current paths, which are used for example for signalling or for the supply of devices for improving the ignition behaviour of SPDs (in particular spark gaps, triggers of spark gaps and the like) and/or for signalling and/or measurement, are generally designed with much smaller conductor cross sections. The supplied devices are not generally short-circuit-proof.
These cross sections are therefore often not short-circuit-proof or overload-proof in the sense of the upstream fuses.
These current paths are therefore to be protected via separate fuses.
Due to the generally limited installation space within surge protection devices, fuses of small size are selected (for example microfuses).
These fuses in the secondary current path do not have the same quenching capability however as the fuses arranged upstream of the surge protection device.
Fuses in the secondary current path are therefore at risk of being destroyed. If these fuses in the secondary path are destroyed, either the entire surge protection device is to be replaced or at least the fuses in the secondary path. This is an involved process, but is also costly in terms of material and time.